HV841
Split Supply Configuration
The HV841 can be used in applications operating from a battery
where a regulated voltage is available. This is shown in Figure
2. The regulated voltage can be used to drive the internal logic
of HV841. The amount of current used to drive the internal logic
is less than 190µA. Therefore, the regulated voltage could easily
provide the current without being loaded down.
Figure 2: Split Supply Configuration
V
EN
= ON
V
EN
= ON 0 = OFF
0 = OFF
Regulated Voltage = V
DD
EL Lamp 1
1
1
2
C
1
V
DD
EL
1
EL
2
10
9
8
7
6
R
SW-OSC
3
4
5
R
SW-OSC
Com
C
2
GND
C
S
L
X
EL Lamp 2
1
D
Battery Voltage = V
IN
HV841MG-G/
HV841K6-G
~
L
X
C
S
1 The bigger sized lamp should be tied to EL1 and the smaller
sized lamp to EL2 terminals (pins 10 and 9 respectively)
Audible Noise Reduction
This section describes a method (patented) developed at Supertex
to reduce the audible noise emitted by the EL lamps used in
application sensitive to audible noise. The waveform takes the
shape of approximately 2RC time constants for rising and 2RC time
constants for falling, where C is the capacitance of the EL lamp,
and R is the external resistor, R
SER
connected in series with the EL
lamp.
Figure 3 shows a general circuit schematic that uses the series
resistors, R
SER1
and R
SER2
, for each of the EL lamps. R
SER1
and
R
SER2
are connected in series with the EL lamp. The audible noise
can be set a desirable level by selecting the resistances for R
SER1
and R
SER2
. It is important to note that addition of these external
resistors will reduce the voltage across the EL lamp, and hence the
brightness of the EL lamp.
Figure 3: Typical Application Circuit For Audible Noise Reduction
ON = V
EN
OFF = 0
ON = V
EN
OFF = 0
Enable 1
R
SER1
Enable 2
1
2
EL Lamp 1
1
C
1
V
DD
EL
1
EL
2
10
9
8
7
6
R
SER2
EL Lamp 2
1
D
+
V
DD
-
C
DD
R
SW-OSC
3
4
5
R
SW-OSC
Com
C
2
GND
C
S
L
X
V
IN
+
C
IN
-
HV841MG-G/
HV841K6-G
~
L
X
C
S
1 The bigger sized lamp should be tied to EL1 and the smaller
sized lamp to EL2 terminals (pins 10 and 9 respectively)
6
NR033106
SUPERTEX [ Supertex, Inc ]
